Kneth's Korner

2014-12-29

Review of WebRTC Integrator's Guide by Altanai Bisht

I picked up the book - not because I'm working on WebRTC or related stuff but simply to get an idea of what this new technology is all about. It's a lengthly book, and the author seems to know every trick of the trade. After finishing the book, I feel that I have a better understanding of what WebRTC (and SIP and PSTN) works - at least on the high level.

One thing I like about the book is that it has many diagrams. As I don't have an in-depth experience before reading the book, the diagrams help me to get a understanding fast.

From a practical standpoint I like chapter 9. It's about native clients of the most widely used platforms today (both desktop and mobile). If you read the book to years after publication, it is probably outdated, and I hope that the publisher will ask the author to update it and publish it at their web site.

Chapter 10 touches a topic which is only going to become larger: WebRTC and TV. Today, we see a shift from broadcasting services (like BBC) to streaming services (like Netflix), and a contemporary TV set (SmartTV) is more a connected computer with a monitor than a receiver of TV signals. Reading chapter 10 is like looking into the future. The book also mention WebRTC in healthcare, and I guess that most countries are discussing how to implement remote healthcare so patients can stay at home.

2014-12-04

Review of JavaScript Promises Essentials

Promises are an old pattern in concurrent programming. In the computer science literature, promises date back to the papers by Friendman and Wise from mid 1970s. Many programming languages have promise - and futures as in Java are a similar idea. A promise is a variable or an object which value is initially unknown and is the result of another task. Modern JavaScript development is highly asynchronous by design: the UI (in the web browser) is updated by calls to the backend using HTTP requests.

JavaScript (ECMAScript to be correct) will soon have promises build into the core of the runtime environment, and promises already exist in many libraries and frameworks. If you haven’t worked with promises in a JavaScript context before, now is a good time to begin. In order to ease the use of promises in JavaScript development, the Promises/A+ standard has emerged.

The book is short and divided in six chapters. The first chapter is an introduction to the state of front-end JavaScript development in general and the asynchronous model in particular. The chapter sets the scene for the rest of the book, and discuss how promises fit well into JavaScript.

The second chapter is written in a very dense format using many bullet lists. You are probably going to read the chapter more than once to get all the information. The good news is that is a lot of information. Chapters 2-4 are a presentation of how to use promises, include error handling.

Chapter 5 is devoted to WinJS - the open source library for development of Windows 8 and Windows mobile applications in JavaScript. Personally, I don’t develop for any of the Microsoft stacks, but the chapter is still useful as it shows how a widely used library is applying the promise concepts.

The final chapter explains how to implement your own promise library. I guess that there exist many in-house JavaScript libraries. If you have such a library, you will find this chapter useful.

In general, the book is well-written. The usage of bullet list many place (and chapter 2 in particular) can make it hard to read the book. Still, any JavaScript developer should read the book and get ready to the great promise of promises. You can find more information about the book here.

2013-12-10

Happy birthday, Grace

Yesterday, Grace Hopper would have turn 107 years old. She was one of the first computer scientists. She worked on compilers but she is probably best known for her development of COBOL. COBOL is one of the first high-level programming languages (FORTRAN is the other one). Back in the 1950s, computers were used as calculators, but COBOL and Grace Hopper shown us that computers can be used for much more that simple calculations. Today, COBOL is still wildly used.

As a tribute to Grace Hopper, I have played a bit with the OpenCOBOL compiler. OpenCOBOL can translate COBOL source code to C and use a C compiler to generate a real executable program. The compiler is licensed under GNU General Public License (version 3), and the runtime is licensed under GNU Lesser General Public License (version 3). That is, OpenCOBOL is free software!

Ubuntu Linux and Linux Mint have packages for OpenCOBOL. Probably other Linux distributions and FreeBSD have packages as well but I haven't checked. The installation (using Linux Mint) is simple:

sudo apt-get install open-cobol

I haven't tried to write software in COBOL. The closest I ever came is that I worked on converting between 4th generation languages (4GL) a few years ago. 4GL programs are often converted to COBOL. But I have written a short program in COBOL:

* Greeting to Grace Hopper

IDENTIFICATION DIVISION.

PROGRAM-ID. greeting.

DATA DIVISION.

WORKING-STORAGE SECTION.

01 WS-TODAY PIC X(21).

01 WS-YEAR PIC 9(4).

PROCEDURE DIVISION.

010-Greet.

MOVE FUNCTION CURRENT-DATE TO WS-TODAY.

MOVE WS-TODAY (1:4) TO WS-YEAR.

SUBTRACT 1906 FROM WS-YEAR.

DISPLAY "Happy birthday"

DISPLAY WS-YEAR

EXIT PROGRAM

.

STOP RUN.

Compiling the program using OpenCOBOL is easy:

cobc -x greeting.cob

and running is easy:

./greeting

I am not going to do a lot of COBOL programming in the future, but it seems to possible to replace old legacy operating systems with a modern platform like Linux.

2013-11-10

Review: Storm - real-time processing cookbook

Quinton Anderson has written a book on the analysis platform Storm and published it at Packt. I have worked a little with Hadoop in the last couple of years, and it is only natural to take a look at the other big data processing platform. Hadoop is a batch processing platform, and Storm is for real-time processing and analysis of data. That means the two projects are not direct competitors, and they might complement each other.

When reviewing a technical book for the general public, it is important not to review the technology but the book. You can easily write a crappy book on excellent technologies while the opposite is very difficult. This review should be read in this context.

The author starts out by explaining how to set up Storm. Storm seems to be quite a complex beast, but Mr. Anderson gets nicely through it. I would have preferred to get an introduction to some of the concept before jumping into the many tasks. But it is my personal preference, and this is a cookbook and not a text book for a university course.

The first couple of chapters is about processing real-time data. Twitter and log files are the canonical examples in this area, and the book utilizes these as well.

One chapter are on how to use C++ and Qt in your real-time data processing. If you think that Qt is about graphical user interfaces, the book will show you that Qt is a lot more. The author is using Qt's non-GUI parts in his processing.

Another chapter is about machine learning. As part of the big data revolution, machine learning has become popular again. Machine learning is a topic that Mr. Anderson is passionate about, and he analyzes in great detail the problem before showing the recipe.

One of the major disadvantages of the book is that the assumptions about the reader are pretty hard. The reader is assumed to know at least about:

Java development using and Maven and Eclipse

Some functional programming

Ubuntu or Debian (or any UNIX) command-line

Web development (HTML, CSS, JavaScript, JSON)

Data modelling experience

A little about NoSQL

This problem does not really from the author but from Storm. But the author might have chosen other examples. The book is not a university text book, and therefore I would like many more references to text book and papers.

There is a lot of source code in the cook. You should really download the examples as some of them are longer than a page. It would be great if Packt would do some kind of syntax highlighting. Most programmers find it easier to read syntax highlighted code. In particular, electronic books (I have read the book as PDF) can easily be colorized!

One of the things I really like about the book is that the author has taken time to craft understandable diagrams. A well-composed diagram is worth many words, and he often sums up the key points in a diagram. In general the author writes in a rather dry or fact based language. But on page 111, you find that the author cannot suppress his humor: "... for automating Clojure projects without setting your hair on fire."

I'm not going to say that Storm is a crappy technology but Quinton Anderson has done the job well by writing a good cook book.

2013-07-05

Recently, Packt Publishing published a book by N. Bhava on ExtJS. It's a fairly short book, about 60 pages long. The idea is to get you started with ExtJS. If you don't know what ExtJS, it is a framework to develop the front-end of web applications. Today, users except web applications to behave must like desktop applications, and a typical web developer is much more like a GUI programmer just a few years ago.
In order to get started with ExtJS, the book is an excellent introduction. By reading the book, it quickly becomes obvious that today's web developers just have a great deal of knowledge of JavaScript, object-oriented programming, HTML and CSS.
JavaScript is a class-less object-oriented programming language. But ExtJS is based on the notion of classes, and they are somehow emulated by plain JavaScript. The author does not go into details - probably due to the limited length of the book. A book of less than 60 pages cannot scratch the surface no matter how great the author is.
Indeed, the book is quite well written, and the flow of the book is fine. But I must be honest, I have tried ExtJS ever before, and the book is too short for my taste. I do like the cook-book like steps in how to install ExtJS. And I like the usage of the browsers' debugger to inspect code and DOM.
The proof-reading of the book could be better. On page 9, the different edition of ExtJS is mentioned twice, and the example of page 35 has an extra </tpl> tag.
If you have another web framework (jQuery UI, YUI, etc.), you will find the book useful. It will give you a clear idea of what ExtJS is all about in a short time. The author emphases early that the strength of ExtJS is it's components. The major components (layout, containers, data, templates, and forms) are discussed. In particular, the layout and data components are nicely explained.
You can find the book here.

2013-06-24

I haven't been developing front-end code in JavaScript for some time. Well, to be more precise: years. Most of my JavaScript code these days is unit tests for a node.js extension, I'm maintaining at work.
Recently, a book on JavaScriptMVC by Wojceich Bednanski was published by Packt. I was curious to see how contemporary web applications are written so I picked up the book. It is a short book - only 124 pages. In the preface, the author sets the requirement of the reader but I think he underestimate what it takes to read the book. In my opinion, the reader is an experience software developer with a sound knowledge of JavaScript, jQuery, and HTML. If the reader hasn't read "the good parts", I would recommend her to do so before reading this book. Furthermore, the reader should not be afraid of the Linux command line. Today, most software developers are trained in object-oriented modeling and design, and the author does assume so.
Through-out most of the book, the reader sees how to develop a simple TODO manager. As TODO managers generally work with dates, the book has a number of assuming dates. On page 21, one sees a task due 1st December 1012.
The approach of the book is to begin by the basic elements and gradually move to more advanced components. If the book has been much longer, I believe that many readers will be lost by this approach. To be fair, a complete example is introduced in the beginning of the book but explanations are coming in later chapters, the reader is left a bit frustrated.
Chapter 2 and 3 are about topics which are invisible to the user of an application: documentation and testing. I agree with the author that these topics are important but I would have preferred them later in the book. Chapter 4 is about how to organize an application. It seems strange that large portion of the example code is commented out on page 51. Moreover, some of the plugins are discussed so briefly that the reader has no clue if there are useful or when to use them.
One of the toughest part of a JavaScript application is to load the required libraries - and in the right order. In my dark past as front-end developer, I wrote a small library for loading libraries. Actually, it is just an excuse to write a graph class in JavaScript. Chapter 5 shows how to do load depending library using JavaScriptMVC. Unfortunately, the author does not explain in details how it works, and the examples are so simple that they have limited value.
I like that the author introduces a complex framework like JavaScriptMVC is a very short book. But I was at times a little confused: does the author only show me the simple solution or best practises? If the publisher has asked for more pages, the author might have had a chance to get deeper into the subject.
You can find the book here.

2012-10-11

Map/Reduce and GNU Parallel

This week I attended a meeting organized by DKUUG.The topic was GNU Parallel and the speaker was Ole Tange - the developer behind GNU Parallel.

To be honest, I have not used GNU Parallel before. Of course, I have heard about it as Ole always talks about the program when I meet him. His introduction to the program was great - enjoy it when DKUUG releases the video.

Simply put, GNU Parallel is able to run tasks in parallel. It can either be running locally or remotely. In order words, GNU Parallel can help you to transform your command-line into a parallel computational engine.

Lately, I have been studying Apache Hadoop. Currently, Hadoop is probably the most popular implementation of the programming paradigm Map/Reduce. GNU Parallel offers a way of specifying the Map component. It is activated by using the --pipe option. On my way home I was thinking on how to implement a simply Map/Reduce based analysis using GNU Parallel.

I have used the On Time Performance data set more than once. It is a good data set as it is highly regular and it is large (5-600,000 rows every month). The data set records every flight within USA, and you can find information about destination airport, delays, and 120 other data points. 6 months of data will result in a 1.3 GB (comma separated value) file.

A simple analysis of the data set is to generate a table of the number of time an airport is used by a flight. The three-letter airport code is unique e.g., LAX is Los Angeles International Airport. It is possible do the analysis in parallel by breaking the data file into smaller parts. This is the map task. Each task will produce a table, and the reduce task will combine the output for each map task into the final table.

In order to use GNU Parallel as driver for Map/Reduce, I have implemented the mapper and reduce in Perl. The mapper is: